Comparison of Available Soil Nitrogen Assays in Control and Burned Forested Sites

Abstract

The existence of several different methods for measuring net N mineralization and nitrification rates and indexing N availability has raised questions about the comparability of these methods. We compared in situ covered cores, in situ buried bags, aerobic laboratory incubations, and tension lysimetry on control and treated plots of a prescribed burn experiment in the southern Appalachians. Environmental influences were examined with soil moisture and temperature measurements. All methods detected significant differences in net N mineralization rates between treated and control plots; P = 0.04, 0.007,0.001, and 0.07 for covered cores, buried bags, lab incubations, and lysimeters, respectively. Mean rates of N mineralization during the growing season were similar for the three soil incubation methods. The laboratory incubation of soil from treated plots produced significantly greater potential nitrification rates than the in situ methods. The four methods were not well correlated; this indicates the need for caution when comparing N transformation data derived from different methods. We conclude that the in situ covered core method is superior because it best incorporates site-specific soil temperature and moisture changes into N transformation measurements.

Effects of fire on soil nitrogen dynamics and microbial biomass in savannas of Central Brazil

“…In this method, overlapping sampling was obtained and allowed the estimation of balances between net mineralization and net immobilization. This method best incorporates temperature and moisture variations into net N mineralization and net nitrification measurements (Knoepp & Swank, 1995). The field-moist soil samples were extracted with KCl 1 N for 1 hour and the inorganic-N concentrations were determined by colorimetry.…”

“…In many of them, net N mineralization increases during the first months after a prescribed fire. This short duration of the fire effect is followed by a period in which the rate of net mineralization returns to prefire levels, and, in many cases, turns to net N immobilization six months to two years after the fire event (Adams & Attiwill, 1986;Knoepp & Swank, 1995).…”

Effects of a Wildfire on Selected Physical, Chemical and Biochemical Soil Properties in a Pinus massoniana Forest in South China

“…The influence of fire on soil total N pools has been inconsistent with reports of increases [60][61][62], decreases [63,64], and no change [65,66]. This inconsistency may be caused by environmental factors, such as soil moisture, leaching, soil erosion, and the soil depth sampled influencing soil N [17].…”

Variation in N2Fixation in Subarctic Tundra in Relation to Landscape Position and Nitrogen Pools and Fluxes

“…The buried bag technique was used (Knoepp and Swank, 1995;Holub and Záhora, 2008) and field triplicates were established for each habitat in July 2011. The uppermost soil layer of 5 cm excluding vegetation was sampled from PP and PC while organic horizon was taken from UT using a soil corer of 5 cm diameter; always in field triplicates.…”